1. Field of the Invention
The present invention relates to a variably focusing mirror driven by electromagnetic force for realizing an automatic focusing and an optical zooming of a miniature camera module, more specifically, to a variably focusing mirror driven by electromagnetic force for realizing a focusing and an optical zooming functions by adjusting a curvature radius of a reflective surface, instead of adjusting the position of a lens group using an electromagnetic driver or a step motor, and an operating method thereof.
In accordance with the recent developments of a communication technology and a digital information processing technology, a handheld terminal technology where an information processing, a calculation, a telecommunication and an image information input/output functions are incorporated, such as a Personal Digital Assistants PDA having a digital camera and a communication function and a handy phone having a digital camera and PDA functions, draws attention. It becomes a gradually recent trend to equip a digital camera module having a high specification due to the developments of a digital camera technology and an information storing technology.
As a mega pixel grade image sensor is used in a digital camera module equipped with a handheld terminal owing to the developments of various technologies, the functions of an automatic focusing and an optical zooming are considered more important than ever. In order to realize an automatic focusing and an optical zooming of a miniature digital camera module, a driver capable of satisfying capabilities such as high speed mobility, a low power consumption and a big displacement, occupying a relatively small volume, especially a driver capable of coping with an increase of displacements required for improving an optical zooming is required.
2. Background of the Related Art
The conventional camera module employs a method for changing positions of a lens group on an optical axis in order to realize an optical zooming and an automatic focusing. FIG. 1 is a conceptual view of a conventional camera module adopting an optical zooming and an automatic focusing using two lens group. When the optical zooming is realized, if a zoom lens group (1) is moved into a predetermined position, an automatic focusing lens group (2) is moved into a predetermined position determined by the position of the zoom lens group to form an image on an image sensor (3). In general, the zoom lens group of the second group lens type camera module with an optical zooming needs a relatively big displacement, and the automatic focusing lens group needs a high speed mobility.
Conventionally, as a method for changing the positions of a lens group, an electromagnetic driver such as a voice coil motor VCM or a driver performing a rotation such as a step motor was employed to linearly move a driving part by rotating a lead screw. The electromagnetic driver like VCM has a limit in increasing a displacement and is disadvantageous in that a power is continuously consumed in order to operate a zooming function. In addition, a driver performing a rotation like a step motor has disadvantages like a complicated mechanism or frictions and noises at a gear when linearly moving a driving part by rotating a lead screw. In addition, a driver using the VCM or a step motor has a difficult in manufacturing a cheap driver because of a complicated structure and decreasing its size. In conclusion, a conventional driver employing a mechanical driving method where a lens group is moved on an optical axis does not satisfy gradually complicated requirements in accordance with the improvements of a zooming and an image quality.